It is presently common for multimode communication devices to roam between networks using a number of access technologies such as Wireless Fidelity (WiFi) and cellular. When connected to a WiFi access point, a Voice over IP (VoIP) call processing system can lose track of a communication device when it roams between WiFi access points. This can happen when the call processing system takes too long to send the communication device a request to re-register with the network. Under such circumstances, a call process system can expend unnecessary resources trying to locate the communication device to complete a call directed to it.